Where is this in the umpire manual?

[NCASAUmp]

I've seen plenty of umpires wearing cell phones on their belts, and it's happening with greater frequency. Now, I'm a rather young umpire, and I'm rather "in" with the tech crowd (running my own servers at home, drooling over the latest Crackberry, etc.). However, my brand new cell phone goes straight into my bag before I start my umpiring duties.

There's nothing that I'm aware of in the ASA book regarding this, but this is just common sense and professionalism. There's nothing in the book that says you can't cartwheel into your positions, either, nor is there anything that says you can't sacrifice live chickens between innings in the appropriate holding position. It shouldn't HAVE to say that.